20i MORPHOLOGY AXD EVOLUTION
present. Thus the Gorilla has the slip to the base of the .fifth metatarsaL and the Orang and Gibbon have the slip to the shaft of the first phalanx.
The flexor brevis digitomm varies. It arises in all from the os calcis, but it may have an additional origin from the tendon of the flexor longus digitorum in any Ape. It has superficial and deep parts inserted as follows:—
— ;vaperS:cia'» part Deep part
Chimpanzee (Hepburn) .. Toes 2 and 3 .. Toes 4 and 5
jSonntag) .. Toe 2 .. .. Toe 3
Gibbon ...... Toe '2 .. ... Toes 3, 4, 5
Orasg (Hepburn and Fick) Three tendons to toes 2, 3, 4
Gorilla (Hepburn'i .. .. ., ,T ,,2,3,4
.. .. Toes 4 and 5 ..Toes 2 and 3
The accessorius is a variable muscle, the literature on each Ape recording its presence or absence. In a Chimpanzee I found only the outer head running from the os calcis and long plantar ligament to the tendon of the flexor longus digitorum.
The lumbricales in all Apes arise from the adjacent sides of two deep tendons. They are inserted as in Man.
The flexor brevis hallucis varies. In the Chimpanzee the inner belly arises from the entocuneiform bone, the sheath of the tendon of the peroneus longus, the capsule of the first metatarso-phalangeal joint and the lower half of the first metatarsaL The outer belly arises from the sheath of the tendon of the peroneus longus and the external long plantar metatarsal ligament. No fibres arise from the cuboid bone. The two bellies are inserted along with the adductores hallucis into the base of the first phalanx of the hallux and the capsule of the